Photographic shutter mechanism



y 15, 1951 F. P. WILLCOX 2,553,394

PHOTOGRAPHIC SHUTTER MECHANISM Filed June 17, 1947 E'eclerieii R VViIIcox Patented May 15,- 1951 UNITED STATES PATENT OFFICE Frederick P.Willcox, Bethesda, Md., assignor to Graficx, Inc., Rochester, N. Y., a.corporation of New York Application June 17, 1947, Serial No. 755,049

2 Claims. 1

This invention relates to photographic apparatus, and particularly toimproved shutter mechanisms for use in photographic cameras or re. latedequipment.

In conventional forms of pivoted blade shut.- tors, particularly of themulti-blade type, the driving of the blades between closed and openpositions is accomplished by the movement of an operating member,usually a rotatably mounted ring surrounding the exposure aperture.Since the pivotal axis of the blades and of the are not concentric, someform of loose connection has always been utilized, most often a pin andslot connection, with a pin .on the driving ring operating in astraighter arcuateslot formed in the material of each shutter blade, .orconversely a pin on each shutter blade operating in a slot formed in thematerial of the driving ring.

Both of the above forms of driving connection are subject to certaindisadvantages, which become increasingly important. as the speed ofmovement of the shutter blades is attempted to be increased. First,there is necessarily a certain amount of play between the pin and itsslot, in order to ensure freedom of movement, which means that theposition of the blade is not always under positive control from thedriving member or ring. Thus the blade may be subject to flutter orerratic movements which reduce the efficiency of the shutter, and evenmultiple exposure where the blades are allowed to rebound aftercompletion of one exposure.

In the second place, the impact force which occurs when the pin contactsthe edge of the slot is localized along a line contact, and the stressapplied to the slot may therefore be so large as to damage the slottedmember or deform it in size and shape. This is particularly true wherethe slot is formed in the relatively thinmaterial of which the bladesare manufactured, the pin being on the blade ring. It has been proposedto reenforce the edges of such a slot in order to strengthen the sameagainst this impact force, but such a solution greatly increases thecost of the blades, as well as adding to their effective thickness andhence complicating the blade mounting and the arrangement oi associatedparts. In the converse case where the blade carries the pin and thedrive ring is slotted, the eccentricity of loading becomesobjectionable.

In order to ensure unimpeded movement of the blades, and to eliminatefriction, it has always been essential in these prior art constructionsthat the driving ring be spaced more or less from the blades themselves.Hence, the force applied to the pin by the end of the slot is notdirected along the median plane of the blade, but is eccentric, and thiseccentricity produces a couple tending to twist the blade out of its ownplane. This tendency is objectionable both from the point of view ofblade life and operating efficienc since the eccentric loading of theblade pivot increases friction between the blades and their guidingsurfaces, wears the pivot bearing and increases the looseness of fitwhich in some measure exaggerates the lack of control of the blades bythe driving member or ring.

It is a primary object of the present invention to provide a shutterblade driving connection which will overcome all of the aboveobjections, and which is particularly adapted to shutters of a highspeed type in which its advantages are most valuable. Specifically, theinvention aims to obtain this object by utilizing a form of drivingconnection which, while compensating for the differences in movementpaths of the shutter blades and the driving member, does so withoutintroducing any undesired looseness or freedom of movement of theblades, hence reducing wear and increasing the possible speed ofoperation without danger of damage to the parts.

An additional object of the invention is to provide a shutter bladedrive which will enable a large part of the effective mass of themechanism to be brought up to a relatively high speed prior to anysubstantial movement of the shutter blades thereby, so that the actualdofling movement of the blades is performed in a shorter space of timethan is required where all of the mechanism, including the blades,leaves its rest position at the same instant.

It is a further object of the invention to provide a shutter in whichthe chance of a rebound of the shutter blades, after completion of thedonning or closing phase of their cycle, is rendered much less likely,and indeed substantially impossible, as compared with prior artconstructions. Such a rebound, of course, is very objectionable,inasmuch as it permits a second exposure of the photographic film atsome time after completion of the first exposure, and while the secondexposure is quite small, in a welldesigned prior art shutter, there areconditions under which it is sufficient to ruin the image.

A still further object of the invention is to provide a shuttermechanism which permits the closing phase of the shutter blades to beaccomplished in .a minimum of time for a given spring tension and clearaperture, and this feature, when coupled with the rapid opening speed ofthe blades mentioned above, provides a shutter whose optical efficiencyis very materially increased. In other words, the time during which theshutter is in its fully open position is a very large percentage of thetotal time required from the commencement of the opening phase to thecompletion of the closing phase.

An ancillary object of the invention is to provide a construction havingthe above advantages with a minimum of complication of the parts,whereby the mechanism may be made rugged and reliable, and at a lowcost.

The above and other objects and advantages of my invention will best beunderstood by reference to the following detailed specification of apreferred embodiment thereof, taken in connection with the accompanyingdrawings, in which:

Fig. l is a front elevational view of a typical form or muiti-bladeshutter embodying the im proved construction, parts being broken away,and the blades being in closed position; and

Fig. 2 is a fragmentary view of a portion of the structure shown in Fig.l, but with the blades in their fully open position.

Speaking generally, I accomplish the objects of my invention byconnecting the shutter blades to the operating member (usually anoscillatable ring) through a pivoted link, the point at which one end ofthe link is pivotally secured to the shutter blade being preferably sochosen that there is obtained a non-uniform transmission of the ringmotion to the blade. More specifically, this point of connection to theshutter blade may be so selected that, during the initial portion of themovement of the ring in opening the blades, the transmission ratio issuch that the shutter blades are moved only a short distance; as thering movement progresses, the extent to which its motion is imparted tothe blades is increased, reaching a maximum when the blades are fullyopen. During the retrograde or closing phase or" the cycle, thetransmission ratio from ringto blades is decreased in a similar wayuntil, when the blades are again fully closed, slight movements of thering have little or no effect on the positions of the blades. As willmore particularly be pointed out hereinafter, it is this latter featurewhich positively prevents any rebound of the ring itself from causing asecondary opening of the shutter blades from their closed positions.

Referring now to Fig. l of the drawings, I have illustrated theapplication of one form of my improved blade linkage to a shutterconstruction of a known type, comprising a shutter casing It providedwith an upstanding outer flange [2 which supports a rotatable coverplate l4 adapted to control the shutter speed in a known manner, andhere illustrated as provided with a serrated edge It and a shutter speedscale l8. Pivotally mounted in casing Hi, as by pivot pins 20, are aplurality (here five) of shutter blades 22, arranged for drivingconnection with an oscillatable ring 24. The manner in which ring 24 isoscillated through a forward and a reverse phase to accomplish theopening and closing movements will now be described, although thismechanism per se is well known in the art.

Pivotally mounted on a mechanism plate 25 is a Winding or cookin lever28, normally biased to a counter-clockwise position by a power spring30, one end of which engages a shoulder 32 on lever 28, the other beingsecured to a fixed part of the casing or plate 26. Pivoted to lever 28,as at 34, is a blade operating hook 36 receiving rithin its notched end38 a lug 40 secured to ring 2-. and passing through plate 26 by means ofa slot 42. A sprin 44 secured to plate 26 serves to maintain hook 35 inengagement with lug 40. When the parts are their Fig. 1 positions, hook36 maintains ring 24 in its most counter-clockwise position, and hencethe blades 22 are kept in closed position, it being understood that thewindin lever 28 is latched in this position by the usual trip lever 44and trigger 46. When trigger 46 is depressed in the direction of arrowat, a shoulder thereon engages and move trip lever 44 against thepressure of a spring 48, and the end of the trip lever is therebydisengaged from a shoulder 50 of lever 28, allowing the same to swingunder the impetus of its spring 30, in the direction of arrow 22 to itsdotted line position. During this movement, hook 35 causes lug 4! tomove first to the right, swinging blade ring 24 clockwise to cause theshutter blades 22 to open the aperture in a known manner, andthereafter, hook 36 pulls lug 4U leftward, returning ring 24 to itscounterclockwise position and closin the blades to complete theexposure.

The angular relation of lever 28 to hook 36, and of the latter to lug40, are such as to prevent any opening of the blades 22 during thewinding or cooking movement of lever 28 in preparation for the nextexposure, in a manner well known in this art. Any known or convenientform of speed control mechanism may be incorporated in the shutter andconnected for control by cover plate i l or otherwise, but as suchmechanism forms no essential part of the present invention, it is nothere described in detail.

In accordance with my invention, I provide between each of the blades 22and the oscillating ring 24 a connection here shown as a link 52 pivotedat its respective ends to the blade and ring. As shown in Fig. 1, whenthe shutter is in closed position, these links 52 he nearlyperpendicular to the ring 24, so that slight movements of the ringproduce little or no movement of the blades. When, however, the ring hasbeen oscillated counter-clockwise to its Fig. 2 position, the axis ofeach link 52 lies nearly tangential to the direction of ring 24, so thatmovements of the ring are transmitted practically directly to theblades.

The manner in which the above construction accomplishes the objects ofthe invention will now be clear. During the initial portion of theshutter opening movement of ring 24, the transmission ratio from ring toblades is practically zero, so that acceleration of the rin under theimpetus of spring 35 and hook 35 is substantially unimpeded by the dragand inertia of the blades themselves. However, this transmission ratiogradually increases to such an extent that, as the blades begin touncover the aperture, the kinetic energy of moving ring 24 readilyovercomes their inertia and moves them very rapidly to the fully openposition of Fig. 2, where it will be observed that motion of the ring 24is being transmitted practically directly to the blades. In a similarmanner, the initial closing movements of the blades are accomplishedquite rapidly because of the high transmission ratio at this time. Whenhowever, the blades have again reached an overlapping or. closedrelationship, the transmission ratio has again been reduced practicallyto zero, with the result that any over-running of the blade ring orassociated driving parts is conveyed only slightly or not at all to theblades; in any event, insufficiently to permit the blades to reopen evenslightly.

The particular arrangement of blade, link and operating ring illustratedin Figs. 1 and 2 has another advantageous aspect. It will be noted fromthese figures that the plane of link 52 lies between the planes of theblade and of the ring; in other words, the blade and ring are separatedby the thickness of link 52. In prior art constructions, such as thoseutilizing a pin and slot connection of the type above mentioned, thereis necessarily some space between the blades and the ring, as otherwisethese parts would contact one another and exert a frictional drag on theblades. Also, such spacing is responsible for the eccentric forces abovementioned which apply an undesirable twisting force or couple to theblades. In the present construction, since the force applied by link 52to blade 22 is applied practically in the plane of the blade, becausethere need be no separation between these parts except such as isnecessary to ensure free movement of the parts, this twisting effort isalmost if not entirely eliminated. It will be noticed, in comparingFigs. 1 and 2, that the direction of link 52 with respect to a linedrawn between its point of attachment to the blade and the pivotal axisof the blade has hardly changed as between shutter open and shutterclosed position; in both cases, the link axis is nearly perpendicular tosuch a line. This means that the link has rotated with respect to blade22 very little during the blade movement, and hence that practically noenergy has been dissipated in frictional movements between these parts;much less, obviously, than would be the case if blade 22 were in facecontact with the underside of ring 24. Moreover, the area of contactbetween the upper surface of link 52 and the under surface of ring 24 isso small that here again there is only a trivial loss in friction. Thus,the object of reducing frictional loss and twisting forces has beenaccomplished in a very expeditious and efiicient manner.

Many changes and modifications may obviously be made in theconstructions above described in detail, without departing from thescope of the invention as defined in the appended claims.

I claim:

1. A photographic shutter comprising a casing having an exposureaperture therein, a plurality of blades pivotally mounted in said casingat points spaced about said aperture for movement to cover and uncoversaid aperture, an operating rin surrounding said exposure aperture andmounted for rotation concentric with said aperture, said ring lyingwholly outside the points of pivotal mounting of said blades, aplurality of links each having one of its ends pivotally connected to acorresponding one of said blades at a point spaced from the pivotalmounting of said blade, and its other end pivotally connected to saidring, the location of the last named pivotal connection being such that,when the blades are in their closed positions, each link liesperpendicular to the direction of movement of said ring, and when theblades are in open position, said links lie nearly parallel to thedirection of movement of the ring.

2. A photographic shutter in accordance with claim 1, in which each ofsaid blades lies in a plane spaced from the plane of said ring, and inwhich each of said links is disposed in a plane between the plane of itscorresponding blade and the plane of said ring.

FREDERICK P. WILLCO-X.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,861,257 Barenyi May 31, 19322,168,893 Aiken Aug. 8, 1939 2,359,116 Johnson Sept. 26, 1944 2,398,567Tranefors Apr. 16, 1946 FOREIGN PATENTS Number Country Date 155,213Great Britain Mar. 10, 1922

